Technical Field
The present invention relates to the field of implantable medical devices, in particular medical devices comprising an artificial contractile structure for occluding a hollow body organ.
Description of Related Art
In order to treat conditions such as urinary incontinence, faecal incontinence, gastro-oesophageal reflux disease and also for the treatment of obesity by gastric banding, medical devices are often implanted into the patient which comprise an artificial contractile structure, often known as a cuff, attached around a hollow body organ such as the urethra, rectum, oesophagus or the stomach. In order to reduce the diameter of the organ in question or to occlude it, the artificial contractile structure applies pressure thereto. Particularly in the case of urinary or faecal incontinence, the contractile structure essentially creates an artificial sphincter which can be opened and closed by controlling the pressure applied by the cuff.
In such applications, it is extremely important to apply this pressure as gently as possible so as to avoid damaging the organ. Currently, this is usually carried out by inflating a tube or balloon-type structure arranged on the inside of the contractile element and which applies pressure on the organ. A commercially successful example of this type of device is the AUS 800 marketed by American Medical Systems, Inc. This device and its predecessors are described in U.S. Pat. Nos. 3,863,622, 4,222,377, 4,412,530, and 4,878,889. When applied for the treatment of urinary incontinence, this device has a silicone pressure regulating balloon implanted in the perivesical space, a silicone control pump implanted in the scrotum or labia and a silicone urethral occlusive cuff wrapped around the bulbous urethra in males or the bladder neck in females. Each component may be filled with saline or radiopaque contrast media, and tubing emanating from each component may be routed between incisions for appropriate connections. The patient operates the device by squeezing the control pump through the scrotal or labial skin, and this action transfers fluid from the cuff to the pressure regulating balloon in order to release pressure on the urethra and permit urination, after which the balloon forces fluid through a restrictor and back into the contractile element so as to re-establish an occlusive urethral pressure within 3 to 5 minutes. Furthermore, the device can be deactivated to allow tissue healing to proceed and urethral edema to subside or before inserting a catheter or other instrument into the urethra.
However, this type of device is extremely complicated to implant since three inter-operating components need to be assembled and filled with fluid in situ, and upon inflation it can fold or change its shape in a non-uniform manner, thereby creating so-called “pillows” which can cause a non-uniform pressure to be applied. Furthermore, they are prone to fluid leakage and may cause urethral atrophy and erosion. Fluid leaks may also cause complications such as post-operative infection requiring maintenance or replacement of the device.
Various attempts have been made in the past at designing non-hydraulic cuffs which do not suffer from the above limitations. For instance, U.S. Pat. No. 6,074,341 describes a medical device comprising a non-hydraulic cuff which is spring-biased in the occluded position. Tension applied to a wire member by the actuator counteracts the spring bias so as to open the cuff. Upon releasing the tension, the spring bias returns the cuff to its occluded position. This arrangement raises safety concerns, since in the case of a malfunction of the actuator the patient would not be able to urinate and would hence require immediate emergency surgery to prevent kidney damage. US 2012/0184980 describes a medical device comprising a different non-hydraulic cuff structure, in which the cuff is formed as a sheath arranged around the urethra, and wherein a tape arranged inside the sheath is attached to an actuator and is pulled so as to tighten the cuff and apply occlusive pressure to the urethra. However this cuff is complicated and bulky. Yet further examples include US 2012/0296157, which describes medical devices comprising extremely simple wire-actuated cuffs, WO13093074, which describes soft rubber cuffs actuated by wires, and EP 1 547 549 which describes cuffs tightened by twisting a pair of wires situated inside the cuff. A gentle, uniform application of pressure to an organ does not appear to be achievable with any of these three latter examples.
An object of the invention is thus to overcome at least partially at least some of the above-mentioned drawbacks of the prior art.